This invention relates to compositions that are mixtures of fluorinated compounds and, more specifically, to mixtures that are substantially constant boiling compositions of difluoromethane and 1,1,1-trifluoroethane or perfluoroethane.
Recently the long-term environmental effects of chlorofluorocarbons have come under substantial scientific scrutiny, because it has been postulated that these materials decompose in the stratosphere under the influence of ultraviolet radiation to release chlorine atoms. Chlorine atoms are theorized to undergo chemical reaction in the stratosphere, which could deplete the stratospheric ozone layer which shields the earth from harmful ultraviolet radiation. A substantial reduction of stratospheric ozone could have a serious deleterious impact on the quality of life on earth. In view of the potential environmental problem associated with stratospheric ozone depletion, there is a need for new materials possessing properties which make them useful substitutes for applications in which chlorofluorocarbons have been used and which are also potentially environmentally safe.
There is a limit to the number of single fluorinated hydrocarbon substances which can be candidates as environmentally safe materials. Mixtures of known materials, however, might be used if the desired combination of properties could be found in a given mixture. Simple mixtures, however, create problems in design and operation of refrigeration and other equipment because of component segregation in both the vapor and liquid phases. To avoid component segregation problems, it is particularly desirable to discover new substantially constant boiling fluorocarbon blends. Such blends would not suffer from component segregation problems. Unfortunately, it is not possible to predict the formation of constant boiling compositions, e.g., azeotropes, thus complicating the search for compositions which possess the desired combination of properties. Accordingly, there is an urgent need for substantially constant boiling compositions that have properties which make them particularly useful as power cycle working fluids, e.g., refrigerants, aerosol propellants, heat transfer media, gaseous dielectrics, fire extinguishing agents, and expansion agents for polymers, such as polyolefins and polyurethanes, that are potentially environmentally safe.